The shortage of water resource and water pollution in our nation has exerted great influence on the residential living quality and national economy. Wherein, the content of heavy metals in water exceeds standard significantly, which not only brings about threats to underground water and the utilization thereof but also brings about potential threats to the treatment and recycle of sewage water, which further limits the rapid development of the social economy. Arsenic, antimony and selenium as the common heavy metal in contaminated water, their contents in the waste water generated in industrial production and ore smelting process are high. Unreasonable disposal and discharge will not only pollute the surrounding drinking water, but also affect the health cycle of ecosystems through accumulation and enrichment of plants and animals.
At present, conventional purification techniques aiming at removing arsenic, antimony and selenium in water include absorption method, ion exchange method, coagulation sediment method, man-made moist land method and biological method and so on. However, by taking comprehensive consideration of industrial development demands, the absorption method becomes the most preferred method for this kind heavy metal removal and purification for it possesses multiple advantages such as being highly effective, low cost, stability, wild applicable conditions and being readily operative. Therefore, how to prepare absorption materials possessing big absorption capacity, excellent hot stability, short hydraulic retention time and wild applicable conditions orientates the absorption technology development in the present stage.
Iron-manganese composite widely exists in nature, which has relatively high specific surface area and surface electronegativity, is an adsorbent with excellent adsorption performance, and has a good development prospect in the adsorption purification of heavy metal in water. At present, the adsorption capacity of the iron-manganese composite oxide to arsenic, antimony and selenium in a water body are respectively 120 mg g−1 (Gaosheng Zhang, Jiuhui Qu, Huijuan Liu, Ruiping Liu and Rongcheng Wu, Preparation and evaluation of a novel Fe−Mn binary oxide adsorbent for effective arsenite removal. Water Research, 2007, 9, 1921-1928), 168 mg g−1 (Wei Xua, Hongjie Wang, Ruiping Liu, Xu Zhao, Jiuhui Qu, The mechanism of antimony(III) removal and its reactions on the surfaces of Fe—Mn Binary Oxide. Journal of Colloid and Interface Science, 2011, 1, 320-326), 41.02 mg g−1 (Szlachta, M. and N. Chubar, The application of Fe—Mn hydrous oxides based adsorbent for removing selenium species from water. Chemical Engineering Journal 2013. 217, 159-168.).
Therefore, only in terms of the absorption performance of heavy metal substances such as arsenic, antimony, selenium and the like, the irregular iron-manganese composite oxide prepared by the traditional method has relatively good adsorption and removal capability on the above three heavy metals. However, there still has a large amount of defects and room for improvement, for example, the specific surface area is small, reactive site is few, and these defects greatly restrict the adsorption performance of the iron-manganese composite adsorption material. Therefore, the study to the structure of the iron-manganese composite material certainly will become the work focus, in order to improve the adsorption performance of the iron-manganese composite material to the maximum extent.
Hollow hydroxyl iron-manganese composite nano-mesoporous material with a cubic structure not only can fully utilize the active groups on the surface of the iron-manganese composite oxide, and also has good dispersibility in a water environment. And, the hollow structure provides a larger specific surface area, so that the active reaction sites of the materials can be more effectively contacted with target pollutants in the solution, then the materials are fully utilized to the maximum extent, and the adsorption performance of the adsorbent is improved.